Heart arrhythmia are conditions affecting the electrical system of the heart, causing irregular heart rhythms. Arrhythmia may originate in the atria or the ventricles of the heart, and they may induce tachycardia (fast heart rate) or bradycardia (slow heart rate). Atrial tachycardia include atrial fibrillation, atrial flutter, supraventricular tachycardia and Wolff-Parkinson-White syndrome. The irregular heart rhythm experienced during atrial fibrillation or other heart arrhythmia may reduce the volume of blood pumped by the heart, and/or may put a patient at an elevated risk for stroke. Ventricular tachycardia include ventricular tachycardia, ventricular fibrillation and long QT syndrome. Bradycardia include sick sinus and conduction block. Pre-existing heart conditions, such as high blood pressure, valvular disease, coronary artery disease and cardiomyopathy, may trigger heart arrhythmia by lowering blood supply to the heart, damaging heart tissue and/or other mechanisms.
Bradycardia may, for example, be treated with a pacemaker. Medical practitioners commonly treat tachycardia, such as atrial fibrillation, via electrical cardioversion with an external defibrillator. An implantable cardioverter defribrillator additionally or alternatively may be utilized. Medical practitioners also may utilize anti-arrhythmics to control the patient's heart rhythm. Furthermore, they may recommend that a patient take anti-coagulants, such as warfarin or aspirin, to thin the blood and reduce a risk of blood clot formation. Serious tachycardia may be treated via ablation of targeted regions of the heart that impede aberrant electrical signals via a band of scar tissue. Patients who have undergone such ablation procedures may require a pacemaker to maintain a regular heart rhythm.
The kidneys may play a role in atrial fibrillation, as well as other heart arrhythmia or other cardio-renal diseases. Numerous academic studies have noted an increase in sympathetic nerve activity during atrial fibrillation. The functions of the kidneys can be summarized under three broad categories: (a) filtering blood and excreting waste products generated by the body's metabolism; (b) regulating salt, water, electrolyte and acid-base balance; and (c) secreting hormones to maintain vital organ blood flow. Without properly functioning kidneys, a patient may suffer water retention, reduced urine flow and an accumulation of waste toxins in the blood and body.
Applicants have previously described methods and apparatus for treating renal and/or cardio-renal disorders by applying energy or neuromodulatory agents, either directly or indirectly, to neural fibers that contribute to renal function. Such energy may, for example, comprise a monopolar or bipolar electric field, a thermal or non-thermal electric field, a pulsed or continuous electric field, a stimulation electric field, a beam of high intensity focused ultrasound, a thermal cooling energy and/or a thermal heating energy. See, for example, Applicants' co-pending U.S. patent application Ser. No. 11/129,765, filed on May 13, 2005; Ser. No. 11/189,583, filed on Jul. 25, 2005; Ser. No. 11/363,867, filed on Feb. 27, 2006; Ser. No. 11/368,836, filed on Mar. 6, 2006; and Ser. No. 11/504,117, filed on Aug. 14, 2006. Additional methods and apparatus for achieving renal neuromodulation, e.g., via localized drug delivery (such as by a drug pump or infusion catheter) or via use of a stimulation electric field, etc, are described, for example, in co-owned and co-pending U.S. patent application Ser. No. 10/408,665, filed Apr. 8, 2003, as well as U.S. Pat. No. 6,978,174.
The energy or neuromodulatory agents may be delivered to the neural fibers that contribute to renal function from apparatus positioned intravascularly, extravascularly, intra-to-extravascularly or a combination thereof. Furthermore, the energy or neuromodulatory agents may be delivered to neural fibers innervating a single kidney, or they may be delivered bilaterally to neural fibers innervating both kidneys. In some embodiments, the energy may initiate denervation or other renal neuromodulation substantially athermally at least in part via irreversible electroporation or via electrofusion. In other embodiments, the energy may thermally induce the denervation or other renal neuromodulation via ablation or other mechanisms. Renal neuromodulation may reduce renal sympathetic nerve activity.
In view of the foregoing, it would be desirable to provide novel methods and apparatus for treating heart arrhythmia.